This study focused on the development of a sensitive enzymatic biosensor for the determination of
pirimicarb pesticide based on the immobilization of laccase on composite carbon paste electrodes. Multi-
walled carbon nanotubes(MWCNTs)paste electrode modified by dispersion of laccase(3%,w/w) within the
optimum composite matrix(60:40%,w/w,MWCNTs and paraffin binder)showed the best performance,
with excellent electron transfer kinetic and catalytic effects related to the redox process of the substrate4-
aminophenol. No metal or anti-interference membrane was added. Based on the inhibition of laccase
activity, pirimicarb can be determined in the range 9.90 ×10- 7 to 1.15 ×10- 5 molL 1 using 4-
aminophenol as substrate at the optimum pH of 5.0, with acceptable repeatability and reproducibility
(relative standard deviations lower than 5%).The limit of detection obtained was 1.8 × 10-7 molL 1
(0.04 mgkg 1 on a fresh weight vegetable basis).The high activity and catalytic properties of the laccase-
based biosensor are retained during ca. one month. The optimized electroanalytical protocol coupled to the
QuEChERS methodology were applied to tomato and lettuce samples spiked at three levels; recoveries
ranging from 91.0±0.1% to 101.0 ± 0.3% were attained. No significant effects in the pirimicarb electro-
analysis were observed by the presence of pro-vitamin A, vitamins B1 and C,and glucose in the vegetable
extracts. The proposed biosensor- based pesticide residue methodology fulfills all requisites to be used in
implementation of food safety programs.